That's why I was asking. :) I think CCK makes a lot of sense for profile fields in the long run. Will CCK be in D6 core though?
No. There is not enough time. Examples: the installer took years to finish and form API was eight months of damned hard work. The new menu system will be about four-five months -- do not forget that I had a skeleton in Brussels (and it was more than proof-of-concept shortly after) and I started on the real thing well before the freeze and still I will be happy if everything will be together before the end of March. Based on the change data API would require, if you starting coding Adrian's data API _right now_ with a speed that would put the split-finger operators of GiTS to shame then you might make Drupal 7. Otherwise even Drupal 7 is out of question. Regards, NK